On Mon, May 22, 2006 at 08:36:39PM -0400, Ryan Flannery wrote: > On 5/22/06, prad <[EMAIL PROTECTED]> wrote: > >this is not openbsd specific, but i wanted to ask people who really > >understand > >the inner workings of programming languages. > > > >suppose that you have 2 conditions A and B where B take a lot of effort to > >determine (eg looking for a string match in a huge file). > > > >either A or B needs to be true before you can execute 'this'. > > > >the 2 if statements below are equivalent i think: > > > >if A or B: > > do this > > > >if A: > > do this > >elseif B: > > do this > > > >now, do they work the same way? > > > >in the second if A is true we don't need to go looking for B (the more > >laborious one). > > > >in the first, do both A and B get evaluated or does A get evaluated first > >(because it is first in sequence) and if it is true, no evaluation of B > >takes > >place? > > > >do all programming and shell languages handle this the same way?
The best thing to do, in any language, is to state what you mean clearly. If you know you want A evaluated first because it's cheap, then do it that way and comment it. // if (A or B), but check A first because B is expensive if A: something elseif B: something end if This works whether short circuit evaluation is in effect or not, and it's clear that you mean it to work that way and why. -- Darrin Chandler | Phoenix BSD Users Group [EMAIL PROTECTED] | http://bsd.phoenix.az.us/ http://www.stilyagin.com/ |
